The present invention relates to a method for detecting a periodically pulsing operating parameter of an internal combustion engine, which includes the steps: detect a measured quantity of the periodically pulsing operating parameter of the internal combustion engine, in order to generate a periodically pulsing measurement signal, discretize the measurement signal in the time range having a fixed time increment, and so, in each case, a number of discrete measured values is obtained for one period of the measurement signal that corresponds to the number of time increments in the period, each measured value being considered representative of the measurement signal in the particular time increment, and determine a mean over the period of the measurement signal by calculating a mean of the discrete measured values. Furthermore, the present invention relates to a device that is designed to implement a method of this type, and to a computer program for executing all steps of a method of this type.
During operation of internal combustion engines, it is necessary to detect various operating parameters, some of which pulse periodically. For instance, it is necessary to detect the air mass flow that is directed into the combustion chambers of the internal combustion engine; this air mass flow pulses due to the discontinuous operation of a piston-type internal combustion engine. Air is drawn in only when one of the intake valves of the internal combustion engine is open. Nevertheless, the air mass flow must be determined as exactly as possible in order to ensure economical and low-emission operation of the internal combustion engine. The operation of a sensor for the determination of air mass flow is described in DE 199 33 665 A1. Further pulsing operating parameters of an internal combustion engine are, e.g., the pressure in a high pressure fuel accumulator or the angular velocity of the crankshaft of the internal combustion engine.
In conventional methods for evaluating a periodically pulsing measurement signal, the measurement signal is detected and discretized using a time frame. In that case, a discrete measured value is assigned to a particular subsequent time increment of the time frame that corresponds to the measured value at the beginning of the time increment. Means of the measured values are then calculated for the two half-waves of a period, with all measured values being weighted equally. Finally, these two means of the particular half-waves of the period are averaged, in order to obtain an overall result.
In the method described in the prior art, an error occurs if, at the beginning of the period or at the end of the period, the boundary of the particular time increment does not coincide with the boundary of the period. This is disadvantageous since it results in an inexact determination of the air mass flow, and so fuel may be metered incorrectly in some circumstances. This may result in unwanted exhaust emissions and uneconomical operation of the internal combustion engine. It is likewise problematic if the pressure in a high pressure fuel accumulator is determined incorrectly since, if an incorrect pressure value is applied, the quantities of fuel that are injected by the injection valves into the combustion chambers differ from the demanded setpoint fuel quantities.